Acute kidney injury (AKI) is characterized by an abrupt decline in kidney function and is an increasingly common condition that is strongly associated with morbidity and mortality. AKI has been estimated to account for $10 billion annually in excess direct medical costs in the U.S. Despite the clinical and public health importance of AKI and a growing population of AKI survivors, the full significance of AKI remains relatively underappreciated. We believe that closing knowledge gaps will improve the care of patients with AKI, by increasing recognition of the condition and follow-up care. Dr. Raymond Hsu, a nephrologist at UCSF, is establishing himself as a young investigator in patient- oriented clinical research in AKI. His prior work has shown that the U.S. population incidence of severe AKI appears to have increased rapidly at a previously unappreciated ~10% per year over the past decade and that the incidence of dialysis-requiring AKI is now higher than the incidence of dialysis or transplant-requiring end- stage renal disease. He has also shown that there is considerable regional variation in incidence of dialysis- requiring AKI around the U.S. which had not been known previously. This K23 proposal builds on this strong foundation with the ultimate goal of developing Dr. Raymond Hsu into a national leader in AKI research. Raymond has assembled a mentoring team of internationally recognized researchers led by Dr. Chi- yuan Hsu, Professor and Chief of Nephrology at UCSF, an expert clinical researcher in AKI and chronic kidney disease (CKD). The co-mentoring team will include: Dr. Alan Go, Director of Comprehensive Clinical Research Unit and Section Chief of Cardiovascular and Metabolic Conditions at Kaiser Permanente Northern California, a renowned expert in kidney and cardiovascular disease research experienced at using Kaiser Permanente's comprehensive clinical data; Dr. Charles McCulloch, Professor and Head of Biostatistics at UCSF, an expert in longitudinal data analysis; and Dr. Neil Powe, Professor and Chief of Medicine at San Francisco General Hospital whose broad research interests in nephrology include patient awareness of kidney disease. Dr. Raymond also has the support from two large NIDDK-funded prospective cohorts, the Chronic Renal Insufficiency Cohort (CRIC) and ASsessment, Serial Evaluation, and Subsequent Sequelae in Acute Kidney Injury (ASSESS-AKI) studies. The project's three Specific Aims are: Aim 1: To determine the independent association between AKI and incident hypertension. Aim 2: To better delineate the impact of AKI on renal function trajectory by comparing three different methods of assessing renal function over time. Aim 3: To determine the level of patient awareness and physician recognition of AKI, and to determine the association between these and follow-up care.